Polycarbonates belong to the group of technical thermoplastics. They find versatile application in the electricals and electronics sector (E/E sector), as a housing material for lamps and for applications where particular mechanical properties are required. A further large field of application are optical data storage means such as the various CD and DVD formats as well as Blu-ray disk and HD DVD and also extrusion applications such as polycarbonate sheets, diffuser sheets for backlighting, LED applications and other display applications or water bottles but also optical applications in the automotive sector, such as glazing, plastic covers, diffuser screens or light conducting elements, collimators, lenses, polymeric optical waveguides and also lamp covers for linear luminaires.
Relevant among the thermal properties of polycarbonate compositions are in particular HDT (heat distortion temperature), ball indentation temperature (BIT) and VST (Vicat softening temperature).
Housing materials for E/E applications, for example smart meters, are recently being expected to meet enhanced requirements, in particular improved heat distortion resistance HDT-A or HDT-B. At the same time, other requirements are demanded such as UV stability, good demolding behavior or flame retardant properties which must in each case be established by the use of special additives. However, these additives result in a deterioration of the thermal properties because they act as internal plasticizers which reduce the glass transition temperatures.
In addition to the thermal properties, the polycarbonate compositions also need to have good processing behavior in injection molding. This relates in particular to the demolding behavior of complex three-dimensional components.
EP 1 925 638 A2 describes the use of a synthetic wax oxidate having a number average molecular weight of 300 to 1000 g/mol and an acid number in the range from 15 to 60 mg KOH/g as processing aid in polar transparent polymers. However, it is the effect of the addition of this processing aid on the transparency of the polymer that is investigated here. Thermal properties such as Vicat temperatures or BIT are not addressed. The effect of the processing aids in opaque compositions is not mentioned either. EP 0 262 566 A1 discloses the use of oxidized polyethylene having a number average molecular weight of 7000 to 15 000 g/mol as a demolding agent in ester-free, thermoplastic, aromatic polycarbonates. EP 0433 723 A1 describes the addition of oxidized polyethylenes having a number average molecular weight of 3000 to 5000 g/mol to aromatic polycarbonate resins comprising styrene-acrylonitrile copolymers or acrylonitrile- and styrene-grafted polybutadienes. However, the molar mass of the polyethylenes of the prior art does not give any indication of their acid number or crystallinity.